Hydrangea paniculata: The bold, brave flowers that can stand up to whatever the British climate can throw at them

Hydrangeas are very useful late-summer shrubs. The typical mopheads, however, are not so easy to grow in the colder parts of our island. That is when and where the white-flowered species Hydrangea paniculata comes into its own.

The wild species comes from Japan and parts of south-eastern China and its flowers are invariably white, but with a tendency to turn pink as they age. They are happy in shady woodland or in open sunny positions, but all hydrangeas give of their best if they are grown in soil that does not dry out. The great value of H. paniculata is that it remains in flower for a very long time, sometimes through to the end of October.

One unusual feature of Hydrangea paniculata is its flower buds, which are completely round, like oversized green drums. The flowers, however, open out as long, conical panicles, which may hang from the branches or grow more upright, according to the strength and thickness of their stems. These panicles have large, sterile florets that attract pollinating insects towards the pollen and nectar of the insignificant fertile flowers.

They are usually scentless, but butterflies, wasps and honey bees nip busily in and out of them. The flower spikes of the wild species are fairly open, but almost all garden varieties are a mass of overlapping sterile florets, presenting a solid cone, slightly reminiscent of a very large lilac, but always white, and opening from green buds.

A stream of new cultivars has been arriving in garden centres on these shores in recent years, from breeders in Japan, France, the Netherlands and the USA. There isn’t a single dud among them — all will grow well in our conditions, flower for many months and give great pleasure.

There are nearly 200 cultivars now in the National Collection of Hydrangea paniculata at Darley Park in Derby. Almost all have massive flower spikes, but some have been developed for their ability to turn unusual shades of pink or crimson with age. Others have been chosen because they remain white right to the end or because the florets are green and slow to turn to white.

Small cultivars are also emerging — Pinky-Winky, now overtaken by newer varieties, is a July-flowering favourite that combines moderate growth with a rich pink colour as it matures. These shorter varieties reach about 3ft in height, whereas some of the larger ones, useful for landscaping, may end up closer to 8ft or 10ft, with vigorous upright and spreading branches if left unpruned.

The RHS four-year trial, organised by Debbie Roe, RHS trials officer, at Bridgewater Garden near Manchester of Hydrangea paniculata cultivars ended last autumn and the great number of Awards of Garden Merit the judges conferred reflects the excitement it generated.

It was an important exercise because it was linked to similar trials in eight European countries, including Belgium, Germany and France, run by the Royal Dutch Horticultural Society under the auspices of the Euro-Trial organisation. Exactly the same 83 cultivars were simultaneously propagated by the Dutch and circulated to all eight nations, so that the trials would have the same starting point and the RHS’s results, together with those from all the other trials, will be published in the Netherlands in a final overall report.

Each of the 83 varieties was represented by three plants: one was hard-pruned to ground level each year in spring, one lightly pruned and one left unpruned. All performed very well.

The results confirmed every gardener’s experience: pruning delays flowering, but the flowers are larger. Unpruned plants bloom sooner and have more flowers, but they are smaller.

The RHS recommends cutting them to the ground every year — some nurserymen do this with a chainsaw — but, whatever régime you adopt, you will not be disappointed: all Hydrangea paniculata varieties are reliable garden plants. The fact that they bloom only on this year’s new growth means that they will flower perfectly even if they are caught by a late frost, too.

The trial judges were told to mark the plants for their vigour and health, the colour of their stems and the size, shape, colour and season of their flowers. They also considered a number of characteristics that many of us would not have considered. For example, the judges looked for plants with strong, sturdy stems, because the large panicles fill up with water in rainy weather and may flop down and be spoiled by contact with the soil.

One very effective way to grow varieties such as Pinky-Winky, the stems of which cannot always bear the weight of its beautiful flowers, is to graft them onto the upright stem of a vigorous variety and grow it as a standard.

With many cultivars of Hydrangea paniculata now available and so many excellent new ones launched every year, it is increasingly difficult to choose between them, but you can be certain that all will be healthy, tough, easy to grow — and beautiful.

This feature originally appeared in the September 9, 2026, print edition of Country Life. Click here for more information on how to subscribe.